The difference is that this election has gotten younger voters excited again. Sanders is seen as unique among a sea of establishment politicians, and his policies have the ability to positively affect issues that my (I'm 32) generation has had a pretty awful time with. So many of us have crippling student loans, and the frustration that the US government has been making money off of students, and not charging interest rates nearly as high to corporate entities, will get voters out. I think that the thing people are realizing, and what has caused Sanders to surge in the polls over the past months, is that we have a chance to finally elect someone who is committed to our interests.
I may be wrong, but the groundswell of support is very real.